Currently, a touch panel, as input medium, is a most simple, convenient and natural means for human-computer interaction.
Reference is made to FIG. 1, a liquid crystal display apparatus with an in-cell touch panel (In-cell touch panel) according to the conventional technology is shown. The liquid crystal display apparatus includes, from bottom to top, a thin film transistor (TFT, Thin Film Transistor) substrate 1, a liquid crystal layer (Liquid Crystal) 2 and a color filter (CF, Color Filter) substrate 3. The TFT substrate includes a first glass substrate 11, and thin film transistors 12 arranged on the first glass substrate 11. The CF substrate includes, from bottom to top, a common electrode 31, a color filter 32, a touch screen 33 and a second glass substrate 34. The touch screen 33 in FIG. 1 may be a self-capacitive touch screen. The self-capacitive touch screen detects capacitance formed by a driving electrode or a sensing electrode and the ground, and position detection is performed based on change in the capacitance caused by a finger touching the touch panel.
During the display of the liquid crystal display apparatus, a liquid crystal display driving circuit switches on the thin film transistors 12 row by row via a gate line, a data line provides a pixel voltage to a pixel electrode 35 of each sub-pixel, and the pixel voltage is provided to the common electrode 31. Reference is made to FIG. 2, an equivalent circuit diagram of a sub-pixel unit in the liquid crystal display apparatus shown in FIG. 1 is shown. An equivalent capacitor Clc is formed by the pixel electrode 35 and the common electrode 31. An electric field in the equivalent capacitor Clc may pass through liquid crystal molecules in the liquid crystal layer 2. The magnitude of the electric field determines an angle of rotation of the liquid crystal molecule, which in turn determines the strength of the light passing through this sub-pixel in a specific direction.
With increased requirement on lightness and thinness for the touch panel, the common electrode is reused as a detection electrode for self-capacitance touch detection. As shown in FIG. 3, a schematic diagram of a common electrode is shown. The common electrode includes multiple block electrodes 36 in four rows and four columns. Each of the block electrodes 36 is connected to a driving chip 37 via a connecting line. The driving chip 37 drives the multiple block electrodes 36 in a time-sharing manner. That is, the driving chip 37 drives the common electrode to a potential required for display during a display stage, and provides a touch detection signal to the common electrode during a touch detecting stage.
However, the common electrode forms multiple parasitic capacitors during the touch detecting stage, which affects the accuracy of the touch detection. Reference is made to FIG. 4, an equivalent circuit diagram of the sub-pixel unit of the touch display apparatus of the common electrode as shown in FIG. 3 is shown. The common electrode is used as a touch detection electrode. Thus, a parasitic capacitor Cmg is formed between the common electrode and a gate line, a parasitic capacitor Cms is formed between the common electrode and a data line, and a parasitic capacitor Cs is formed between the common electrode and an outline of a screen body. The parasitic capacitors would interfere with the touch detection.